The present invention relates to a magnetic temperature sensing device for rotatably moving parts, of the type comprising at least one electromagnetic field source element associated to said rotatably moving part and a magnetic field sensor element associated to a fixed part to measure parameters of a magnetic field determined by said magnetic field source element, said parameters of the magnetic field being a function of the temperature of said rotatably moving part.
Measuring the temperature of rotating parts, such as rolling elements or shafts, has always been difficult, due to the impossibility of wiring a sensor positioned on the moving part.
Of particular interest, for instance, is monitoring the temperature of motor vehicle tires, even when said motor vehicles are moving, both for general maintenance purposes, and for safety purposes when the motor vehicle travels at high speed. It is therefore important that the driver be aware at all times of the temperature of the tires, which may dramatically influence the behavior of the motor vehicle.
Several methods for monitoring tire pressure and temperature are known. Typically, a complex wiring technique is employed, or else transmitters and receivers of electromagnetic waves which require power supplies and antennas.
U.S. Pat. No. 4,570,152 discloses a temperature measuring system in tires whereby a plurality of magnetic nails are inserted in the tread of a tire at determined points. A magnetic field sensor is then mounted on a non-rotating part of the vehicle in proximity to the tire and it is used to detect the magnetic pulses generated by the plurality of rotating magnetic nails. If tire temperature grows, the heat thereby generated decreases the magnetic field generated by the magnetic nails.
Such a system, however, requires the insertion of extraneous bodies into the tread and a considerable proximity of the sensor element to the tread, to detect magnetic field intensity variations in a precise manner.